1. Field of the Invention
The present invention relates to a compressor for a refrigeration system and, more specifically, to improvements in the dimensional relation between the recesses and a discharge port of a bearing member in a compressor for a refrigeration system.
2. Description of the Related Art
A general rotary compressor shown in FIG. 8 for use in a refrigeration system comprises a compressing mechanism 21, an electric motor 22 and a sealed case 20 containing the compressing mechanism 21 and the electric motor 22. The electric motor 22 has a rotor 24, a drive shaft (crankshaft) 2 fixed to the rotor 24 to drive the compressing mechanism 21. The compressing mechanism 21 has a pair of cylinders 1 and 1'. The drive shaft 2 is extended through the cylinders 1 and 1'. Rollers 10 are placed in the cylinders 1 and 1', respectively. The rollers 10 roll along the inner surfaces of the side walls of the cylinders 1 and 1', respectively.
A main bearing member 3 and an auxiliary bearing member 3' are disposed contiguously with the pair of cylinders 1 and 1', respectively. The bearing member 3 and the auxiliary bearing member 3' are basically similar in construction. Therefore only the bearing member 3 is shown in FIG. 9 and only the bearing member 3 will be described. As shown in FIG. 9, the bearing member 3 has a flange 5 joined to an end surface of the corresponding cylinder 1 (FIG. 8), and a bearing part 6 supporting the drive shaft 2. As shown in FIGS. 10 and 11, a discharge port 4 is formed through the flange 5. FIG. 11 is a fragmentary longitudinal sectional view taken on line XI--XI passing the center axis 6c of the bearing part 6 and the center axis 4c of the discharge port 4 in FIG. 10. As shown in FIG. 9, a discharge valve element 7 is attached to the flange 5 of the bearing member 3 to open and close the discharge port 4. A valve holder 12 is attached to the flange 5 to limit the opening of the valve element 7. A recess 8 corresponding to the discharge valve element 7 is formed in the flange 5. As shown in FIG. 11, a portion of the bottom surface 80 of the recess 8 around the outlet end of the discharge port 4 is raised to form a valve seat 9.
The conventional compressor for a refrigeration system as mentioned above has the following problems. As the thickness T (FIG. 11) of the valve seat 9 increases, the amount of the refrigerant remaining in the discharge port 4 increases after the completion of a discharge stroke. The increased amount of the refrigerant remaining in the discharge port 4 reduces the coefficient of performance (COP) of the refrigeration system and increases noise generated by the operating compressor. However, the thickness T of the valve seat 9 is equal to the thickness H of the bottom wall of the recess 8 or is greater than the same to prevent cavitation. Therefore, if the thickness T of the valve seat 9 is reduced simply, the thickness H of the bottom wall of the recess 8 is reduced accordingly. If the thickness H of the bottom wall of the recess 8 is reduced, the deflection of the bottom wall of the recess 8 due to the difference between pressures acting respectively on the opposite sides of the bottom wall of the recess 8 increases.
If the bottom wall of the recess 8 is deflected, the refrigerant leaks to further reduce the COP and it is possible that the bearing members 3 and 3' are broken. With a view to forming the valve seat 9 in a sufficient thickness T and surely preventing the deflection of the bottom wall of the recess 8, the diameter B of the discharge port 4 and the thickness T of the valve seat 9 are determined so that the ratio T/B&gt;0.3 in the conventional compressor.